In women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That’s a result of fetal exposure to testosterone.

My 13 year old nephew, while staying with us over the summer, brought up a fact that he had heard and then read about. Apparently, he purported, the length of ones index finger as compared to ones ring finger could differentiate most men from most women. This has been well documented over the years but I had not been aware of the full details as I saw in this particular study. You can imagine how perplexed and confused my nephew was when his theory of my being masculine seemed to fail when he measured my fingers over and over and found my index and ring finger were of equal length suggesting that I was more woman than man.

The whole basis of the study was based on levels of in-utero exposure to androgens or estrogens during pre-natal development. Other meaningful relations were able to be concluded as well; including relations to spatial skills as well as language and artistic aptitudes vs. mathematical and logical/reasoning aptitudes. All of these relations appear to be a direct correlation of the brain’s exposure to male or female hormones pre-natally. I’ll save the good stuff for when you check out these links…

Let’s just say that both my wife and I were surprised at the results we discovered for both her and I. The shorter length of her index finger as compared to her ring finger also related directly to the relations drawn for her left-handedness as a possible result of higher testosterone levels pre-natally and correlated well to other aspects that concern her as well.

“if a mother is stressed during the early stages of pregnancy, she will release an adrenaline related hormone into her own bloodstream and that of her unborn baby. This hormone, called androstendione, is structurally similar to testosterone, the male hormone. If the baby carries “XY” chromosomes and is destined to become a male, testosterone needs to be active when the Central Nervous System (including the hypothalamus) is being formed. This is the only way that the CNS “knows” to develop along male lines. Because the stress hormone seems to bind to the receptors that would normally be receiving testosterone, there is the delay or blockage of the effectiveness of testosterone, even if it is plentiful.”

“…The present data support the hypothesis that exposure of pregnant rats to environmental stressors modifies the normal process of sexual behavior differentiation in male fetuses by decreasing functional testosterone and elevating androstenedione levels during prenatal development. During stress conditions plasma testosterone emanating from the gonads decreases while adrenal androstenedione rises. The molecular structure of the two androgens, being very similar, it is postulated that the two hormones compete for the same receptor sites. Since androstenedione is a less potent androgen than testosterone, the decrease in male copulatory ability and increased lordotic potential seen in the prenatally stressed animals of the present study would be expected. The relative difference in potency between testosterone and androstendione has been repeatedly demonstrated.

It is therefore possible that while the body and organs of an animal can be a “male,” the brain can coincidentally be “female.”

Another, more recent article, has proven this relationship to yet another degree further and I highly recommend a review of it!